Defined in header
Interprets an unsigned integer value in the string
Discards any whitespace characters (as identified by calling
isspace()) until the first non-whitespace character is found, then takes as many characters as possible to form a valid base-n (where n=base) unsigned integer number representation and converts them to an integer value. The valid unsigned integer value consists of the following parts:
- (optional) plus or minus sign
- (optional) prefix (
0) indicating octal base (applies only when the base is 8 or 0)
- (optional) prefix (
0X) indicating hexadecimal base (applies only when the base is 16 or 0)
- a sequence of digits
The set of valid digits for base-2 integer is
01, for base-3 integer is
012, and so on. For bases larger than
10, valid digits include alphabetic characters, starting from
Aa for base-11 integer, to
Zz for base-36 integer. The case of the characters is ignored.
Additional numeric formats may be accepted by the currently installed C locale.
If the value of base is 0, the numeric base is auto-detected: if the prefix is
0, the base is octal, if the prefix is
0X, the base is hexadecimal, otherwise the base is decimal.
If the minus sign was part of the input sequence, the numeric value calculated from the sequence of digits is negated as if by unary minus in the result type, which applies unsigned integer wraparound rules.
pos is not a null pointer, then a pointer
ptr, internal to the conversion functions, will receive the address of the first unconverted character in str.c_str(), and the index of that character will be calculated and stored in
*pos, giving the number of characters that were processed by the conversion.
|str||-||the string to convert|
|pos||-||address of an integer to store the number of characters processed|
|base||-||the number base|
 Return value
The string converted to the specified unsigned integer type.
- std::invalid_argument if no conversion could be performed
- std::out_of_range if the converted value would fall out of the range of the result type or if the underlying function (std::strtoul or std::strtoull) sets errno to ERANGE.
 See also
| converts a string to a signed integer |
| converts a string to a floating point value |